Fredo had committed the unforgivable offense, the injury that can never be made whole. He had betrayed one of his own.

This, more than any laws that might have been broken, gets to the core of the anguish and uproar over John Walker Lindh.

My son asked me the other day why Lindh was being treated differently from the other Taliban. Didn't they all commit the same offense? Why might Lindh spend his life in jail but not the other fighters? And why is everyone so angry at someone who seemed such a minor (some might say irrelevant) figure in the war?

I could have explained that fighting against one's own country - if that is what Lindh did - is considered the highest crime in the land, that treason is the only criminal offense specifically mentioned in the U.S. Constitution.

But there was a simpler answer.

"Betrayal," I said.

Treason, conspiring to kill an American abroad, providing support to a terrorist organization that results in American deaths - they are the legal expressions of something much more personal, an offense that stirs some ancient ganglia deep inside us, triggering emotions that reach back to the beginning of time.

"Elemental to every social group is the sense of moral obligation to each other," said James Quesada, an anthropology professor. "Betrayal induces an almost primordial reaction. That basic bond of trust has been severed."

In virtually every culture's story about Earth's first man and woman, the couple inevitably falls from grace after betraying the gods. The Bible tells the tale of Adam and Eve, who were tossed from Eden for betraying God's trust. For many Christians, that betrayal is known as original sin because it has stained all human souls ever since. It was the one sin even God couldn't forgive.

We reserve special contempt for those who turn on one of their own. In the story of Jesus' death, it is Judas the betrayer more than Pontius Pilate the condemner who is the more despicable figure.

In Shakepeare's "Julius Caesar," the one line everyone remembers is in the raspy last words of the great leader: "Et tu, Brute?" Brutus's betrayal is the true tragedy in the story, more than the bloody assassination itself.

In modern times, Linda Tripp became the target of ceaseless, hateful criticism and derision not so much because she revealed Bill Clinton's sordid romps in the Oval Office but because she betrayed a friend to do it. (As for Clinton's own betrayals, they will garner more space in his obituary than his accomplishments.)

The Enron story, too, has captured the nation in great part because it's a tale of betrayal: A beloved boss and civic leader named Ken Lay, trusted beyond reason by his employees, sells them out and destroys their lives.

"In all closed groups, there's a shared identity," said Nancy Shepper-Hughes, a UC Berkeley anthropologist. "There's the notion of insiders and outsiders. You can lie, cheat and steal among the outside group, but there's a morality that applies within the group that can't be broken."

Lindh was an insider who went over the wall. He became the other. He embraced a moral code that spit in the face of everything the group held dear.

He is not unlike a lot of people at 20, an age of rebellion. But he rebelled against an America that has pulled itself more tightly together than at any time since World War II. Verbal dissent is barely tolerated at the moment, so it is no surprise that 28 percent of the people in a recent poll support executing Lindh if he is found guilty of providing support to Osama bin Laden's army, even if he didn't personally harm another American.

No matter what happens in the courts, Lindh has already been sentenced. Fair or not, true or false, he will bear the stain of betrayal forever.